Combination telephone and telegraph exchange system



,May 25, 1937. B. B. JACOBSEN 2,931,434

COMBINATION TELEPHONE AND TELEGRAPH EXCHANGE SYSTEM Filed Feb 28, 1935 I lNl E TOP 8. B. JACOBSEN BYj'%/JM ATTORNE V Patented May 25, 1937 UNITED STATES COMBINATION TELEPHONE AND TELE- GRAPH EXCHANGE SYSTEM Bent Biilow Jacobson, Aldwych, London, England,

assignor to Western Electric corporated, New York New York Company, In- N. Y., a corporation of Application February 28, 1935, Serial No. 8,592 In Great Britain June 18, 1934 4. Claims.

This invention relates to telegraph exchange systems and to telephone systems in which at least two subscribers are provided with facilities for telegraph communication over the normal 5 telephone line and connecting devices.

One of the objects of the invention is to provide novel and improved means for releasing telegraph connections in such systems which insure that complete release takes place at two interconnected stations.

One feature of the invention comprises tele graph station equipment soconstructed and arranged that when installed and connected up for use, release of a telegraph connection is caused'by a signal similar in character to the telegraph signals used, but longer in duration than the longest similar telegraph signal.

Another feature comprises telegraph station equipment which is so constructed and arranged L that when installed and connected up for use,

release of said equipment from a telegraph conf nection can be controlled. from the station itself or from a remote point characterized in this, that the equipment is adapted when releasing in response to a signal from a remote point to take less time to release than when release is initiated by the station itself.

These features are particularly useful in automatic exchange systems in which unattended teleprinter service is given.

This is due to the fact that an unattended called station may receive dialing tone very soon after the calling subscriber has cleared his end of the connection. The dialing tone is liable to cause operation of the teleprinter relay and this will prevent the teleprinter stop device from operating. 1

By-means of the present invention, the calling subscriber in clearing his own end of the con- 40 nection automatically and completely clears also the unattended called'end of the connection.

Another object of the invention is to provide arrangements whereby change-over from telegraphy to telephony during a call is facilitated, and

'45 stations are automaticallyput into condition to receive and make telephone calls if subscribers do not operate their release keys after a telegraph communication.

A further feature of the invention comprises a telephone system in which at least two stations are provided with facilities for telegraph communication over the normal telephone lines and connecting devices, and in which, after a normal telephone connection has been set up between two such stations, the connection can by after completing telegraph transmission over a agreement be manually changed over at each station to the telegraph equipment characterized in this that change-over to the telegraph equipment is dependent on replacement of the telephone receiver or the like on the switch-hook. 5

Yet another feature comprises a telephone system in which at least two stations are provided with facilities for telegraph communication over the normal telephone lines and connecting devices, characterized in this that when a connection between two such stations is connected to the telegraphequipments, change-over to the telephone sets can .be caused merely by removing the telephone receiver or the like at each station from the switch-hook.

Another feature of the invention comprises a telephone system-in which at least two stations are provided with facilities for telegraph communication over the normal telephone lines and connecting devices characterized in this that if,

connection between two attended stations, neither operator performs any release-initiating operation whatsoever, release of the connection will automatically take place and both stations will be ready to make or receive telephone calls.

Another object of the invention is to provide means whereby preferential calls, such as trunk calls, can be extended to stations engaged on telegraph connections. It is clear that it is impossible for instance tobreak in upon a telegraph connection over telephone exchange lines and offer a trunk telephone call verbally in the usual way, since the station telephones are not connected up. It would not be economic to provide telegraph offer facilities to trunk operators, 35 but with the present invention the release signal used in a telegraph connection is of a character which can be easily and cheaply simulated by stations outside the connection for breakdown 4 purposes. 0

According to another feature of the invention, therefore, telegraph and telephone systems of the type to which the invention relates are provided with means whereby a station not included in a telegraph connection is enabled to break down a telegraph connection.

According to another feature of the invention, release of a telegraph connection can be initiated by a pulse of alternating current transmitted under control of a station which is or is not a party to the connection. 7

One embodiment of the invention will now be described with reference to the accompanying drawing which shows the substation circuits of a telephone subscriber provided with teleprinter facilities.

The teleprinter equipment at each substation comprises a voice frequency teleprinter unit I similar to that disclosed in the copending application of A. M. Searle et al., Serial No. 607,040 filed April 23, 1932, a subscribers telephone set 2 and teleprinter 3; only those parts of units I and 2 are shown which are relevant to the invention. The circuit consists of five relays R (ringing and line relay), M (motor relay), W and S (delayed stop relays) and T (tone sending relay) The circuit further contains two non-locking keys P (Print) and C (Clear line), a battery 5, a two-position locking key AU with contacts a1, a2 and or which are made when the key is set for attended operation and contacts in and us which are made for unattended operation, and various resistances, condensers and a lamp l2. The circuit is shown connected to a subscribers line L1, L2 coming from an automatic telephone exchange, which is not shown. All relay contacts in the circuit are shown in the rest condition which they assume when no current passes through the relay windings. The key contacts of the non-locking keys P and C are shown in the unoperated position while the contacts of the locking key AU are shown in the position they assume when the key has been set to the attended position.

In the circuit as shown, the subscribers telephone station is connected to the exchange lines L1 and L2 via the upper back contact and armature of relay M and the subscriber can receive and send telephone calls in the ordinary way.

If the subscriber wishes to establish a teleprinter call, the procedure is as follows: the subscriber establishes a normal telephone connection with the required subscribers; the subscribers agree verbally to change the connection into a teleprinter connection and each .momentarily operates the key P at his own station. Thereby, a circuit is established which energizes the relay M and which may be traced from the positive pole of battery 5, closed contacts of key P, resistance 1, through the lower and the upper windings of relay M, motor 6, to the negative pole of battery 5, the relay windings respectively being of high and low resistances. The current in this circuit is insufficient to start the motor 6 but will cause relay M to operate. At the lower armature and contact is established a circuit which holds the relay M operated independently of key P and which may be traced from the positive pole of battery 5, lower armature and contact of relay M, contact and armature of relay S, resistances 8 and 1, lower and upper windings in series, to the negative pole of battery 5. The operation of relay M disconnects the subscribers line L1 from the subscribers telephone equipment 2 and connects it to the line transformer winding 4 of the voice frequency teleprinter unit I. When relay M operates, relay R is placed in series with the subscribers telephone set 2 across the subscribers line in a circuit traceable from line conductor L1, through the winding of relay R, contact oz of key AU, through to the subscribers telephone set and back to the line conductor L2; and relay R. operates on part of the subscribers line current. Part of the subscribers line current flows through the teleprinter unit transformer winding 4 in a circuit traceable from line conductor L1, upper armature and front contact of relay M, resistance 9, through the line transformer winding 4 and back to the line conductor L2. The

resistance 9 limits this current and insures that sufficient current is available for the operation of relay R. The closure of the lower armature and contact of relay R has no effect in the present condition but the opening of the upper armature and contact prevents the operation of relay T via the lower armature and contact of relay M. The closure of the lower armature and contact of relay M causes relay W to operate in a circuit traceable from the positive pole of battery 5, lower armature and contact of relay M, through the winding of relay W, through the winding of printer magnet l0, contact and lowermost armature of relay T, to the negative pole of battery 5. The opening of the armature and back contact of relay W prevents the operation of relay S. A stable circuit condition has now been reached, relays R, M and W being operated.

The subscribers line is connected to the teleprinter unit line transformer winding 4 which is shunted by the subscribers telephone set 2 in series with R. In order to complete the switching operation, the subscriber must replace his telephone receiver. This has the effect of breaking the current which previously flowed through the subscribers set 2, thereby causing the relay R to release. The release of R closes the operating circuit for relay T which operates after a delay in a circuit traceable from the positive pole of battery 5, lower armature and contact of relay M, upper armature and contact of relay R, through the winding of relay T, resistance ll, back to the negative pole of battery 5. The closure of the lower middle armature and contact of relay T completes a circuit which supplies sufficient current for the operation of the teleprinter motor 6, the circuit being traceable from the positive pole of battery 5, lower armature and contact of relay M, contact and armature of relay S, lower middle armature of relay T, through the upper, or low resistance, winding of relay M, through the winding of motor 6 and back to the negative pole of battery 5. Relay W and magnet H] are now held by current from a low tension battery eliminator in the unit I, the original operating circuit being open at the contact and the lowermost armature of relay T.

Teleprinter communication can now take place, transmission being controlled by teleprinter contacts TC, and unit l transforming the received voice frequency signals into direct current impulses to printer magnet it. The station is now ready to receive and transmit telegraph messages and this is indicated by the lamp l2 which operates in parallel with motor 6. The other subscriber has independently made the same operations at his station.

When the circuit is no longer required for teleprinter operation, three different cases may arise:

1It is required to resume telephony 2-It is required to clear the connection between the two subscribers 3-The circuit is left idle 1. If it is required to resume telephony, the subscribers merely lift their telephone receivers or microtelephones from the switch-hooks and the telephone line is immediately switched back to the telephone set 2.

When the receiver is lifted, the relay R operates on part of the subscribers loop current as before. The closure of the lower armature and contact of relay R, completes a circuit which short-circuits the upper, or low resistance, winding of relay M, thereby causing relay M to release, the original operating circuit of relay M now being so changed ill) as to trace from the positive pole of battery 5,

lower armature and contactof relay M, contact and armature of relay S, lower middle and innermost armatures and their respective contacts of relay T, lower armature and contact of relay R, contact al of key AU, upper inner armature and contact of relay T, through the winding of motor 6 and back to the negative pole of battery 5. The lower armature and contact of relay M open and the power or battery supply 5 is disconnected, causing the release of relay W and, after a delay, of relay-T.

The release of relay M also causes the upper armature of the relay to return to normal thereby connecting the telephone set directly across the subscribers line. Relay R is now short-circuited and releases. The circuit is now in exactly the condition it was in before thesubscriber pressed the print key P.

2. It is required zoczem'me'eonnecnon between the subscribers If the subscribers have no need for telephonic communication after the exchange of teleprinter messages, the connection may be cleared by either oneor the other of the subscribers by operating the non-locking key C (clear line) until his own teleprinter motor stops running, viz., until the lamp I2 is extinguished. By pressing C, the contacts 01 are opened. These contacts 01 are in series with the teleprinter transmitting contacts TC and. when opened cause the transmission of a signal lasting as long as the contacts remain open. At the other station, which is identical, this signal is received and causes the current normally flowing from the set through the windings of relay W and magnet I supra.

I to disappear thereby releasing relay W. The release of relay W closes a circuit at the relay armature and back contact which supplies current to the relay S causing the latter to operate after a delay of about half a second when contacts 02 areclosed at that station or one second when 02 areopen; I At the station which is effecting the clearing and at which key C is operated, the relay S will,

therefore, operate after approximately one seconds delay, while at the distant station at which it is assumed that key C is not operated, only half a second is required. Operation of relay S at each station breaks the power supply to the motor 6 and relay M releases thereby disconnecting the power supply. The relays S and T each release after a short delay (caused by the condensers i3 and M) and the circuit is restored to the rest condition with the subscribers set connected across the line ready to receive further calls.

3. Release of the connection when the circuit is left idle without either key C being operated feature is known and is disclosed in U. S. Patent 1,834,349 granted to R. D. Salmon on December 1, 1931. In Fig. 1 it is represented by X. When the motor current ceases the relay M will release and the circuit will be cleared as under Case No.2, Since the subscriber was forced to replace his telephone receiver on the switch-hook in order to be able to use the teleprinter, the advantage is gained that whenever the teleprinter circuit is cleared tne line will be made free for a further call. Without this feature the subscriber would have to remember to replace his telephone receiver after switchingover to the teleprinter and to the voice frequency teleprinter unit I ture disengages its contact teleprinter relay lower-middle armature and its contact on relay 3 to :lift the receivierofi before switching back to the telephone if telephony is to be resumed.

' Unattended reception of a teleprinter call When the subscriber leaves his office unattended, by operating the locking key AU to the u position, he may put the circuit in a condition in which it will connect the teleprinter equipment to the telephone linein response to the normal telephone ringing signal.

Consider now the circuit shown with the modification that all contacts belonging to the AU key are operated to the u position. The relay R in series with the condenser I5 is bridged across the subscribers line in parallel with the subscribers telephone set. When connection with this subscribers line is required, ringing current is transmitted to the subscriber in the ordinary way and causes the bell of the subscribers telephone station to ring; at the same time ringing current flows through condenser and relay R and the relay vibrates.

The armatures of relay R intermittently engage their respective contacts and thereby operate relay Min a circuit traceable from thepositive pole of battery 5, contact a of key AU, lower armature and contact of relay R, resistance 1. through the lower and the upper windings in series of relay M, through the winding of motor 5 and back to the negative pole of battery 5. The lower armature of relay M engages its contact and thereby locks up relay M in a circuit traceable from the positive pole of battery 5, lower armature and contact of relay M, contact and armature of relay S, resistances 8 and I, through the lower and the upper windings in series of relay M, through the winding of motor 6 and back to the negative pole of battery 5. At the lower armature and contact of relay M power is applied At the upper armature and contact of relay M, the teleprinter unit is connected across the subscribers line L1, L2 thereby closing the loop and giving the ordinary answer indication to the automatic exchange, which in turn stops the ringing tone so nection and serves to indicate that a voice frequency teleprinter has engaged the distant end of the line.

Relay W energizes over the lowermost armature and contact of relay T as before i and thereby insures that relay S does not operate. Over the lower armature and contact of relay M, relay T energizes through the normally made contact over the upper armature and contact of relay R when ringing ceases. Relay T, however, does not operate until about two seconds have elapsed due to the presence of the condenser l4 and resistance II. This signal is similar to the release signal but will not have any releasing effect on the distant teleprinter when connected up.

When relay T operates and closes its upper outer armature and contact, the teleprinter unit ceases to transmit tone. The lowermost armabut relay W will now normal rest condition teleprinter set through I0. The engagement of the be held operated by the current flowing from the T short-circuits the resistances 1 and 8 thereby providing a low resistance supply circuit for the motor 6 which consequently starts up, the circuit being traceable from the positive pole of battery 5, lower armature and contact of relay M, contact and armature of relay S, lower middle armature and contact of relay T, through the upper winding of relay M, through the winding of motor 6 and back to the negative pole of battery 5. The circuit is now completely ready to receive a message.

The calling subscriber, on hearing the teleprinter tone, should start his own. teleprinter as described above and should then check that he is correctly connected by using the answer back device which is normally provided on the teleprinter. While signals are being received, relay W will release and operate in. accordance with the signals. The inter-engagement of the armature and back contact of relay W will, therefore, tend to make relay S operate, but the operating time of relay S exceeds the longest possible continuous teleprinter signal so that S will not operate. The resistance l6 prevents any cumulative effect of si nals on the condenser l3. The operating delay of S in practice should. exceed one hundred and forty mili-seconds and is usually made between one-quarter and one-half a second.

When the calling subscriber has finished his message, he clears the connection by operating his C key until the teleprinter motor at his own station stops as indicated by the lamp l2. This causes a long voice frequency signal to be sent into the line and at the distant station the relay W remains released during this signal and relay S operates, thereby releasing the circuit as described above. As previously stated, the length of signal required to release the station which sends the release signal is made to be approximately twice the length required for the other station. This is obtained by means. of contacts 02 of the clear line key C. When the contact is open, the operating delay of relay S is doubled due to the inclusion of the resistance H3 in the supply circuit of relay S.

This method of clearing an unattended station gives clearing of both ends. at nearly the same time; in other words, the clearing is effected in the same way as if the subscribers line had been used only for telephony.

This method offers a further advantage; the telephone exchange may, if required, clear a connection simply by sending a long tone of frequency similar to the carrier frequency or if instead of the resistance 9 a network is substituted having a high impedance at the ringing frequency then in the attended condition and with the voice frequency teleprinter connected to the line, the receptionv of ringing current at the subscribers station will cause relay R to vibrate and the interengagement of the lower armature and contact of relay R will, as described above, short-circuit and thereby release relay M and consequently the whole teleprinter equipment will be released.

This feature should be useful when an exchange has a preferential call to offer to one or the other of two subscribers engaged in a teleprinter call. The exchange breaks in on the connection in the ordinary way and hears the teleprinter signals on the line. The ordinary method of advising the subscribers to abandon. their connection in favor of the preferential call cannot be used and it is hardly practicable to equip the exchange with apparatus for sending voice frequency teleprinter signals. However, with the present proposals by sending a carrier tone signal or by ringing on the subscribers line, the exchange mayclear the connection and then ring the subscribers number again.

In the circuit shown, the reception of a ringing signal at a station in the unattended condition causes the called subscribers line to be closed without delay. It is obviously possible to combine the features of the present circuit with those of the pending application of A. M. Searle et al., supra; for instance, by introducing a delay relay controlled by the lower armature and contact of relay R and having a contact replacing contact of relay R, the circuit for locking the delay relay in the unattended condition will require prolonged ringing before the teleprinter unit is connected to the line. It is, of course, similarly possible to introduce the non-metering feature described in the said specification. Various combinations of the features of the two circuits are possible and are obvious to those skilled in the art.

A circuit could, for instance, easily be derived from the present circuit in which a calling subscriber ringing up another subscriber with the intention of delivering only a teleprinter message, could, by sending manually or automatically, a code signal, connect the distant subscribers voice frequency teleprinter unit to the distant end of the connection to the temporary exclusion of the telephone set at the station.

The circuit at the distant station would be one in which the subscribers normal telephone bell has been removed from the circuit, and in which a bell is actuated in a special local circuit only if after the lapse of a certain period no special teleprinter code signal has been received.

If an ordinary telephone subscriber rings up a station equipped in this way, the call will' be effected in the usual way except for a short delay in the application of audible ringing signal at the called end.

If a subscriber calls up intending to establish a teleprinter connection then, immediately on hearing the ring-back tone, he should send a code signal which prevents the called subscribers special bell from being actuated and which, at the same time, completes the connection to line of the called subscribers teleprinter equipment.

The switching operations in a station being called would be as follows:

Ringing current would be received at the called station by a relay in response thereto, the called station would send a ringing trip signal back to the exchange and connect the teleprinter unit to the line via a condenser without closing a direct current exchange loop. If the calling subscriber requires only a teleprinter connection he will send a code signal, the reception of which will close the called subscribers loop and complete the connection of the teleprinter. If the code signal is not sent, the teleprinter will not be completely connected to the line or will only be connected operatively for such a short time that no message of any length could be received. It is, therefore, not possible for the calling subscriber to avoid the metering of an effective call.

If the calling subscriber requires a telephone call he will, of course, not send any code signal and at the receiving station a local ringing circuit will be established after a short delay, and the teleprinter unit will be disconnected from. the circuit. The subscribers telephone station is connected across the line in the normal way and response to the call will trip the local ringing circuit, and complete the subscribers loop.

If the call is not answered, the local ringing circuit will be interrupted with along delay.

The code signal which converts the call into a teleprinter call may be quitesimple, but should be such that it cannot accidentally be initiated by speech currents.

The type of circuit just described tends to give preference to the teleprinter facility in so far as the teleprinter circuit may be established with shorter delay than that suffered by telephonecalls. The circuit is, therefore, particularly suited for lines which are, in the main, used for voice frequency teleprinter working.

The equipment used for this service would not need any switch for conditioning the set to attended or unattended but would have keys for print and clear.

What is claimed is: A

1. In a telephone exchange system adapted for transmitting telegraph messages, a line circuit, a plurality of stations connected to said line circuit, telephone equipment and telegraph equipment at each of said stations connected to said line circuit, manually operated switching means included in said telphone equipment for establishing a connection between said stations over said line circuit, other manually operated switching means for preparing a connection between said telegraph equipments over said line circuit, automatically operated means in said telegraph equipment arranged to complete the connection between said telegraph equipment when said first mentioned manually operated means is restored to normal, a release key arranged when opened to transmit a signal longer than the longest similar telegraph signal to the telegraph equipment at each of said stations, corresponding slow-acting relays at each of said stations, a source of current normally flowing through eachv of said relays, transformer means at each of said stations responsive to said long signal for causing the normally flowing current to disappear and to thereby cause the release of said slow-acting relays and the subsequent release 01' said telegraph connection.

2. In a telephone exchange system adapted for transmitting telegraph messages, a line circuit, a plurality of subscribers stations connected to said line circuit, a telephone subset including a telephone receiver and a switch-hook and a. telegraph printer set at each of said stations connected to said line circuit, means responsive to the removal of said receiver from said switchhook for establishing a connection between said telephone subscribers sets and their respective lines, key operated means for preparing a connection between said telegraph printer sets, said prepared connection being completed when said telephone receiver is restored to said switchhook, and means at each station responsive to the removal again of said receivers for effecting a transfer of the communication connection of the line circuit to said telegraph printer sets to said telephone subscribers sets.

3. In a telephone exchange system adapted for transmitting telegraph messages, a line circuit, a

plurality of stations connected to said line circuit, a telephone subscribers set and a telegraph printer set at each of said stations connected to said line circuit, means responsive to the removal of said receiver from said switch-hook for establishing a, connection between said telephone subscribers sets and their respective lines, key operated means for preparing a connection between said telegraph printer sets, said prepared connection being completed when said telephone receiver is restored to said switch-hook, and means at each station responsive to the removal again of said receivers for eifecting a transfer of the communication connection of the line circuit to said telegraph printer sets to said telephone subscribers sets, other means for establishing, after communication has terminated, a line condition longer in duration than the longest condition used in telegraph signaling, and release means at each of said stations responsive to said line condition of long duration for automatically dis- I connecting an established connection after completing telegraph transmission over a connection between said stations when the attendants at said stations fail to operate said releasing means or restore said receivers to said switch-hooks.

'4. A telephone and telegraph exchange system comprising a plurality of stations, a transmission circuit extending from each of said stations, telephone and telegraph equipment at each of said stations, said telephone equipment being normally connected to its associated transmission circuit and said telegraph equipment being normally in engageable relation with said associated transmission circuit, signaling means at each of said stations for originating a connection to any one of said other stations, an exchange whereat said transmission circuit terminates for efi'ecting connections between the transmission circuit of a calling station and the transmission circuit of a called station in response to the signaling means at said calling station, a plurality of manually operated switching means at each of said stations, each arranged for disassociating said telephone equipment from its associated transmission circuit and. for associating, in place of said disassociated telephone equipment, said telegraph equipment and vice versa, one of said switching means being employed when the station is attended and the other of said switching means being employed when the station is unattended, a switch and slow operating means responsive to said switch, at each of said interconnected stations for disassociating the telegraph equipment from said transmission line, either of said switches at said interconnected station, when operated, being arranged to initiate a disconnection and said slow operating means responsive to said initiating switch being arranged to require more time to operate to thereby effect the disconnection than the corresponding slow operating means at the other of said interconnected stations, and signaling means at said exchange for first sending a warning of disconnection to two interconnected stations and then effecting the disconnection between said interconnected stations whenever desired.

BENT BULOW JACOBSEN. 

